This invention relates to compositions which exhibit controlled release properties and a process for making the same.
The controlled release of active substances in accordance with the present invention is attributable to the gas deposit effect of the instant compositions. The term "gas deposit effect" as used in this application refers to the essentially uniform evaporation of an active substance from a composition, such as a molded article of unsaturated polyester resin, over a long period of time whereby a useful concentration of the active substance may be maintained in the ambient air over a prolonged period of time.
The term "active substance" as used in this application refers to any composition which has a finite vapor pressure at room temperature and which exhibits some useful property when present at some minimum concentration in ambient air. Included in the category of active substances are perfumes, deodorants and insecticides, and the like.
Molded articles which exhibit gas deposit effect are discussed in German Patent Disclosure No. 1,694,240. Such articles, which may be in the form of slabs, spheres, ribbons, tablets, or bars and which are based upon O, O-dimethyl-O-(2,2-dichlorovinyl)-phosphoric acid esters and unsaturated polyester in conjunction with vinyl compounds which are polymerizable therewith, accomplish the gas deposit effect by including in the molded articles, solid filling materials, optionally in conjunction with liquid filling materials, while the weight ratio of active substance to unsaturated polyester is from about 1:4 to about 2:1. The disclosed filling materials include fibers of glass, sisal, hemp, nettle, coir, flax and other vegetable products and synthetic fibers.
It is also known that solid filling materials may be utilized which are mineral in nature, such as titanium oxide, iron oxide, kaolin, quartz, and other inert materials. Liquid filling materials which are suitable for the mentioned purpose are compositions which have a carrier effect, such as dioctyl phthalate, chloroparaffin, and alkyl sulfonic acid arylester.
German Patent Disclosure No. 1,230,259 describes formed masses which exhibit long-lasting insecticidal effect and which are characterized by the combination of a volatile, organic phosphorous compound of a given composition useful as an insecticide, and a thermoplastic, water-insoluble, macromolecular substance such as polyvinyl chloride or mixed polymers containing vinyl chloride. Thus, the absorptivity of the polyvinyl chloride for the active insecticidal substances is limited. If the polyvinyl chloride masses are to be capable of absorbing sufficient insecticide, the corresponding mixtures have to be provided with considerable quantities of softening agents. If insufficient softening agent is present, the content of active substances in the surface of the molded articles declines very rapidly, a limited amount active substance migrates from the interior of the molded articles, and the mass quickly becomes ineffective.
The "cage effect," as a result of which the active substance diffuses only slowly from the deeper layers to the surface, exists to a large extent in the case of duroplastic molded articles, which contain no filling material. Molded articles of duroplastic materials, which contain solid filling materials, as described in German Patent Disclosure No. 1,694,240, in particular in the form of fibers, display a relatively uniform release of the active substance to the surroundings, in a concentration that is effective, and the release takes place over an adequately long period of time. As is also customary and required in the case of unsaturated polyester resins when fibers are to be introduced for reinforcement purposes in the form of non-wovens or fabrics, the fibers have to be free from alkali and provided with a finish for adhesion improvement. The manufacture of the molded articles provided with non-wovens or fabrics made of fibers is relatively expensive. In addition, the fibrous non-wovens or fabrics cannot be added in any desired small increment.
Thus, an object of the present invention is the preparation of molded articles which exhibit gas deposit effect, through the copolymerization of unsaturated polyesters with vinyl compounds polymerized therewith, in the presence of an active substance and at least one solid filling material, with substantially reduced costs and without loss of effectiveness.